Date of Award

Spring 2020

Document Type

Open Access Dissertation

First Advisor

Xuewen Wang

Abstract

Overweight and obesity is becoming more prevalent in adults across the United States. Overweight or obese adults are at an increased risk for the development of cardiometabolic disorders. Glycemic variability has recently been introduced as a sensitive measurement of glycemic health as it incorporates oscillations in glucose concentrations over an extended period. Further, evidence has suggested that glycemic variability plays a pivotal role in the induction of oxidative stress commonly found in adults diagnosed with cardiometabolic disorders. Physical activity (PA) and exercise have been utilized as therapeutic treatments for overweight and obesity related complications. Therefore, the overall goal of this dissertation was to investigate the relationship between PA with glycemic variability and oxidative stress, and to examine the influence of exercise training on glycemic variability and oxidative stress in nondiabetic overweight or obese adults.

Three studies were conducted utilizing different designs to (study 1) inspect the current findings linking the relationship between sedentary behavior and physical activity (PA) with, and the influence of exercise on, continuous glucose monitor (CGM) assessed glycemic variability, (study 2; n=28) examine the cross-sectional relationship between objectively measured sedentary time and PA with glycemic variability and oxidative stress, and (study 3; n=8) evaluate the impact of a 12-week aerobic exercise intervention on glycemic variability and oxidative stress. The first study was a critical review of the

literature, while the second study utilized baseline data collected from the Weight Outlooks by Restriction of Diet and Sleep (WORDS) and the Aerobic Treadmill Exercise and Metabolism (A-TEAM) studies, and the third study utilized data collected for individuals that completed the A-TEAM study. For study two, objective assessment of sedentary time and PA was performed, while for study two and three glucose concentrations and glycemic variability were assessed via CGM and oxidative stress assessed as nitric oxide and myeloperoxidase concentrations in human serum (WORDS) or plasma (A-TEAM).

The first study found that

a relationship between sedentary behavior and PA with glycemic control and glycemic variability exists in non-diabetic and diabetic adults. However, there were differential findings when examining the effect of a single bout of exercise or repeated bouts of exercise on glycemic control and glycemic variability between populations, while exercise training improved glycemic control and glycemic variability in type 2 diabetic adults. In the second study, a relationship was observed between PA minutes and energy expenditure of varying intensities with glucose concentrations, but not glycemic variability, and myeloperoxidase concentration, while fasting glucose concentration correlated with nitric oxide and myeloperoxidase concentrations, and the oxidative stress ratio in non-diabetic overweight or obese adults. The third study found that, although myeloperoxidase concentration decreased and the oxidative stress ratio improved, glucose concentrations and glycemic variability did not change following exercise training in non-diabetic overweight or obese adults. Yet, CGM placement at post-intervention, as well as average total daily mealtime changes, may have influenced our findings.

Overall, this dissertation found that a relationship exists between PA with glucose concentrations and oxidative stress. However, glycemic variability may not be positively influenced by exercise training in non-diabetic overweight or obese adults even in the presence of improvements in biological markers of oxidative stress. Collectively, habitual PA may influence glycemic variability differently than structured PA, known as exercise, in our participants. However, these findings are speculative and further research is needed in this population.

Rights

© 2020, Joshua Robert Sparks

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